The invention relates to a medical instrument for cutting and bipolar coagulating tissue in the human or animal body.
Such an instrument is disclosed in DE 197 00 605 Al. Such instruments are used in minimally invasive surgery for cutting tissue in human or animal bodies. The known instrument of DE 197 00 605 A1 comprises scissor arms spread apart to opposing sides which are pivotal with respect to one another. Each scissor arm comprises a cutting edge where the cutting edges slide across one another when pivoting the scissor arms. Tissue is to be mechanically cut with this configuration of the scissor arms.
The scissor arms each comprise a bending portion at their proximal ends over which a slide tube can be slid by actuating a handle at the proximal end of the instrument. This causes the scissor arms to be urged radially toward one another out of their spread position for cutting tissue. When retracting the slide tube, the scissor arms are resiliently spread apart. Such an actuating mechanism for medical pincers is also disclosed in U.S. Pat. No. 5,334,198.
In a first embodiment of the above-mentioned instrument, the scissor arms are configured without a linkage, i.e. the scissor arms are not connected to one another and are also not otherwise guided during the pivot motion. Because of this, the pivoting arms are spread or bent transversely to the axial direction of the scissor arms, especially for hard tissue, for example vessels. The shearing effect of the two cutting edges sliding past one another is no longer sufficiently present, because the cutting edges pass by one another without contact. This has the disadvantage that the cutting effect of the instrument is insufficient.
In a further embodiment of the known instrument, the scissor arms are interconnected with a link bolt about which the two arms are pivotal with respect to one another. Compared to the unconnected configuration, this embodiment represents an improvement with respect to guidance of the scissor arms during rotation, however, a spreading of the arms transversely to the cutting direction cannot be completely avoided with this linkage. In minimal invasive surgery, a miniaturised construction as far as possible is required, so that the scissor arms are often very thin. Since the scissor arms are only held together in the region of the link bolt, the link joint cannot always prevent a spreading of the scissor arms transversely to the cutting direction in the region of the distal ends of the arms. If the bolt is to hold the two scissor arms pressed closely to one another, it must be fixed to the scissor arms without play, which cannot be achieved in miniaturised construction with sufficient stability over longer duration.
A further problem results when the instrument, as foreseen in the known instrument, is to be configured not only for mechanical cutting, but also for bipolar coagulation of tissue. To allow bipolar coagulation, the two scissor arms must be configured as electrodes for receiving high frequency current. One scissor arm is connected to one pole of a high frequency voltage source and the other arm connected to the other pole, so that the two scissor arms carry different electric potentials. This in turn requires that the two scissor arms be insulated with respect to one another at least in the regions where they contact, so that current can flow to the distal ends of the scissor arms.
However, when the bolt also provides the pressure for urging the two scissor arms together, as in the known instrument, it must be form-fit or screw-connected to the two scissor arms, and therefore must be formed of metal. Problems of insulation then arise in the region of the link pin, such that a short circuit or leakage current can arise in this region. The current flow can then not be established to the distal ends of the scissor arms. Even if the metal bolt is provided with an insulation layer, leakage currents cannot be completely avoided. In addition, the insulation layer can wear off during use of the instrument, so that a sufficient insulation of the scissor arms cannot be reliably ensured.
Separable cutting elements are also known which are linked in a type of key-hole connection. This configuration also has the disadvantage that the scissor arms are not sufficiently guided and secured against spreading apart. A sufficient insulation of the scissor arms is also not reliably guaranteed.
The object of the present invention is therefore to provide an improved guidance of the scissor arms in a medical instrument of the mentioned type.
According to the present invention, an instrument for cutting and bipolar coagulating tissue in the human or animal body is provided, comprising:
a shaft having a distal and a proximal end;
a handle arranged at the proximal end;
a first and a second scissor arm arranged at the distal end, the first and second scissor arms being pivotal about a stationary pivot axis arranged at the scissor arms, the two scissor arms being configured as electrodes to be supplied with high frequency current, wherein contacting regions of the two scissor arms are electrically insulated, and each of said first and second scissor arms comprising a cutting edge, said cutting edges slide across one another when pivoting said scissor arm,
wherein at least one of said scissor arms comprises at least one bracket connected thereto which at least partially extends over an outer side of said other scissor arm.
The at least one bracket connected to one of the scissor arms and at least partially extending over the outside of the other scissor arm has the advantageous effect that the other scissor arm overlapped by the bracket is urged by the bracket toward the one scissor arm comprising the bracket or at least prevents a spreading apart of the two arms. Thus, it is ensured that the cutting edges are always in slide contact one another even when cutting harder tissue, especially vessels. The bracket thus provides the necessary retention of the two scissor arms, where the applied pressure achieved by the at least one bracket is more effective than the pressure achieved with the link bolt, because the bracket offers a larger pressing surface and in addition is dispaced from the pivot axis, as opposed to the known linkage. The pressing surface of the bracket is located closer to the distal end where the danger of spreading is the greatest.
In the instrument according to the present invention, not only is the mechanical cutting effect improved by the guidance, but, the scissor arms are additionally interconnected by a link, this link is relieved of stress, because the link no longer provides for holding the scissor arms together.
The link provided only serves the purpose of defining a pivot axis about which the two scissor arms are pivotal with respect to one another.
The suitability of the present instrument as a bipolar coagulation instrument together with a linked connection of the scissor arms is highly improved, because a link pin can be used for the linkage made of an electrically insulating material, for example ceramics, because this linkage need not provide the pressure holding the scissor arms together, but is substantially force free. In this manner, an electrical insulation of the two scissor arms can be reliably ensured in the region of the linkage.
A further advantage provided by the invention is that the scissor arms can be configured to be easily separated despite their guidance.
In accordance wit h the present invention, a bracket is to be understood as a portion of the scissor arm, independent of its form, arrangement or material, which starting from this scissor arm extends over the outside of at least a portion of the other scissor arm. Thus, this other arm is at least partially enclosed or clampable between the one scissor arm and this portion. It will be understood that the pivot motion of the scissor arms remains smooth, i.e. no substantially increased friction is caused by the bracket.
In a preferred embodiment, the at least one bracket comprises an extension in transverse direction to a longitudinal axis of the scissor arms such that it extends at least partially over the other scissor arm even in a maximally spread operational position of the scissor arms.
When the scissor arms are spread far apart, for example for cutting thick tissue or thicker vessels, the advantage is that a retaining effect of the scissor arms is achieved by the at least one bracket even when beginning the cut, so that a spreading or bending of the scissor arms transversely to the cutting direction is avoided even when starting the cut.
In a further preferred embodiment, the at least one bracket is wedge-shaped at a free end.
When the scissor arms assume a spread position in which the at least one bracket does not engage with the other scissor arm, this feature has the advantage that the introduction of the other scissor arm between the one scissor arm and the at least one bracket is improved. It is also made possible to urge the two scissor arms together with increasing pressure when closing the scissor arms along the inclination of the bracket.
Moreover, in a further preferred embodiment, the pivot axis is formed by a pin, which is releasable from at least one of the scissor arms.
This pin can thus be seated loosely in a respective bore of the one or the other scissor arm, without having to be press fit, screw connected or otherwise connected in fixed manner. In the present instrument for providing bipolar coagulation, this feature has the advantage that the pin can be made of an insulating material, for example ceramic or plastic, because the pin is not subjected to friction or even to shearing or compressive forces.
In a further preferred embodiment, the at least one bracket is arranged distally of the pivot axis.
This arrangement of the at least one bracket is of particular advantage, because the effective cutting region of the scissor arms is also at the distal side of the pivot axis and the tendency of the arms to spread apart transversely to the cutting direction is the largest there.
Additionally or alternatively, the at least one bracket can be arranged proximally of the pivot axis.
Particularly preferred is the provision of at least one bracket at the distal side and at least one further bracket at the proximal side of the pivot axis.
In the configuration with at least one bracket at the distal side and at least one bracket at the proximal side of the pivot axis, the mentioned pivot connection between the two scissor arms with the pin is completely relieved of stress. This is because the forces acting on the scissor arms at the distal side of the pivot axis and also the forces acting on the scissor arms at the proximal side of the pivot axis, which would cause a spreading of the scissor arms transversely to the cutting direction or transversely to the axial direction of the arms, are taken up by the two brackets and thus not by the link pin.
In a further preferred embodiment, each scissor arm comprises at least one bracket, and/or one of the scissor arms or both of the scissor arms comprise at least two axially spaced brackets.
In a further preferred embodiment, the at least one bracket is formed integrally with the associated scissor arm.
The stability of the instrument in the region of the scissor arms is further improved with this feature.
In another preferred embodiment, the at least one bracket becomes disengaged with the other scissor arm in a spread position going beyond the maximally spread operational position and the scissor arms in this spread apart position are separable from one another.
The separability of the scissor arms has the advantage of easier cleaning of the instrument in the region of the scissor arms after use. In particular, remaining pieces of tissue or blood collected between the scissor arms can be easily and completely removed. The separability of the scissor arms in this configuration is also particularly simple to manipulate, because the scissor arms only need to be opened to the mentioned spreading position until the at least one bracket releases the other scissor arm. A particularly simple separability of the two scissor arms also results in combination with the abovementioned configuration, where the two scissor arms are pivotal relative to one another about a pivot axis, the pivot axis being formed by a pin which is releasable from at least one of the scissor arms. In the operational state, the scissor arms are secured to one another against undesired separation, so that no further securement means are needed in the region of the pivot axis or the pivot pin.
In a further preferred embodiment, the scissor arms comprise an elastic bending portion at their respective proximal ends, where the bending portions are pushed together by axially shifting the tubular shaft over the bending portions. The scissor arms are thereby pivoted from their spread position into their closed position and vice versa.
This type of actuation for opening and closing the scissor arms, which is known from U.S. Pat. No. 5,334,198, leads to a constructively simple actuator mechanism for the instrument.
As already mentioned, the scissor arms are configured to be electrodes supplied with high frequency electric current. In this manner, the instrument is suited not only for mechanical cutting but also for coagulation as a bipolar coagulation instrument.
The regions of the one scissor arm and the regions of the other scissor arm which contact one another are electrically insulated so that the present instrument is suitable as a bipolar coagulation instrument. Bipolar coagulation has the advantage that the current flow is limited to the region between the scissor arms having different potentials.
Further advantages can be taken from the following description and the attached drawings. It will be understood that the above-mentioned features and those to be discussed below are applicable not only in the given combinations, but may be present in other combinations or taken alone without departing from the scope of the present invention.
An embodiment of the invention is illustrated in the drawings and will be discussed in more detail in the following description.